Patients with juvenile periodontitis (JP) were grouped into one of the two recognized forms of the disease: a localized form affecting incisors and first molars (LJP) and a generalized form affecting more than 14 teeth (GJP). The role of the neutrophil in the etiology and pathogenesis of LJP has recently been recognized. Experiments aimed at confirming previous information related to neutrophil chemotaxis defects in LJP were performed. Additional experiments aimed at demonstrating significant differences in phagocytosis of bacterial spores and inducing spore germination were also completed. Age- and sex-matched healthy subjects were used as "internal" controls (experiments run concomitantly). Peripheral blood neutrophils from 29 LJP, 24 GJP and 24 healthy subjects were assessed for chemotaxis. This assay was performed in a Boyden diffusion chamber using 10(-8) M N-formylmethionylleucylphenylalanine as chemoattractant. A chemotactic defect was defined being 2 standard deviations below the mean of healthy subjects. Twenty-three of 29 LJP (79%) and 14 of 25 GJP (58%) had a neutrophil defect. Peripheral blood neutrophil phagocytosis assays were performed in vitro using radiolabeled bacterial spores [45Ca]Bacillus cereus. Eighteen of 29 LJP (62%) and 7 of 24 GJP (29%) had a phagocytic defect. Neutrophil-induced spore germination assessed in vitro showed that 13 of 20 LJP (65%) and 3 of 8 GJP (38%) had this defect. These observations indicate that patients with JP have abnormalities in neutrophil functions of chemotaxis, phagocytosis and spore germination.